Penile prosthesis

ABSTRACT

A penile prosthesis is disclosed that can alternate between an erect and flaccid state based on the shape memory properties of an exoskeleton that is responsive to increases and decreases in temperature. The exoskeleton consists of a shape memory alloy, such as nitinol, which in the erect configuration can radially expand and resist axial loads and buckling forces during coitus. The shape memory alloy is temperature-tuned to undergo a change to an erect state under external application of heat and can revert to a flaccid state with cooling below resting penile temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority under 35 U.S.C. 119 to U.S.provisional patent application Ser. No. 61/629,531, filed Nov. 21, 2011,and entitled “Penile Prosthesis,” the contents of which are hereinincorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates generally to penile prostheses in the treatmentof erectile dysfunction and more specifically to the radial expansionand changes in configuration from flaccid to erect state to simulate anerection. The proper functioning of the device relies on the ability ofthe prosthesis when implanted in the corpus cavernosum to expandcross-sectionally and straighten to the erect position during sexualintercourse.

BACKGROUND

Erectile dysfunction (ED) is a multifactorial disease that affectsapproximately 30 million American men and is continuing to increasealong with the upsurge in diabetes, hypertension and cardiovasculardisease. When first line and second line medications such as thephosphodiesterase 5 inhibitor class of medications or direct injectionsfail, surgical implantation of penile prostheses offers a permanentsolution. Surgical implantation of prostheses is a known practical meansof treating erectile dysfunction.

Two broad classes of penile prostheses are known in the prior art, theinflatable prosthesis and the semi-rigid prosthesis. The inflatablepenile prosthesis aims to closely parallel a natural erection byshifting fluid from one area of the device, usually a reservoir, to thecylinders within the corpora cavernosa under hydraulic pressure to mimicthe erect state. It relies on a closed system of reservoirs, pumps,valves and hydraulic pressure to produce a simulated erection sufficientfor coitus. Consequently, the surgical implantation of this device ismore complex is prone to mechanical failure. Indeed only 67 to 88% arefully functional at 10 years, (Selph et al. Penile prosthesis infection:approaches to prevention and treatment, Urol. Clin. N. Am. 2011; 38(2):227-235). The advantages of the inflatable prosthesis are that itappears more physiologic and does not exert constant pressure onsurrounding tissues when in the flaccid state reducing the risk oferosion.

In contrast, the semi-rigid strikes a balance between being rigid enoughfor penetration, but malleable enough to allow positioning downwardswhen not in use. The advantages are that the device is simple, reliable,involves a smaller dissection, has fewer parts, and requires minimaldexterity to use. The disadvantages are that it appears constantlyerect. It exerts more force on the surrounding tissues and has increasedrisk for erosion.

Thus there is a need for a surgical solution for men with refractoryerectile dysfunction that appears as physiologic as possible, yetremains discrete. The penile prosthesis we propose meets the criteriafor a discrete, physiologic-appearing, penile implant that can be usedto treat ED. It has the advantages of the malleable prosthesis in thatit only requires implantable cylinders and has no scrotal pump orabdominal reservoir, but then also has the advantages of an inflatablepenile prosthesis in that with application of heat can produce asimulated erection with expansion of the cylinders. It is different fromexisting thermal-based solutions in that this device takes advantage ofthe fine-tuned properties of commercially available nickel-titaniumalloys, notably their hysteresis and reliable shape-memory properties,as opposed to phase changes.

SUMMARY

In one aspect of the invention, a penile prosthesis that is implantablein the corpus cavernosum is disclosed wherein the prosthesis has acylindrical outer contour along its longitudinal axis, is comprised of ashape memory alloy, and has a dimension that enlarges in response to anincrease in temperature around said prosthesis.

In a second aspect of the invention, a penile prosthesis that isimplantable in the corpus cavernosum is disclosed wherein the penileprosthesis is comprised of a single portion of a shape memory alloyhaving a cylindrical shape. The prosthesis comprises a backbone runningalong a longitudinal axis of the device and has loops circumferentiallyextending from the backbone. The device widens radially whilemaintaining a substantially cylindrical shape at or above a transitiontemperature.

In this aspect of the invention, the shape memory material comprisingthe apparatus is a nickel-titanium alloy. Doping with copper or chromiumto adjust its response to temperature can further modify thenickel-titanium alloy.

In a third aspect of the invention, a penile prosthesis that isimplantable in the corpus cavernosum is disclosed wherein the penileprosthesis is comprised of a single portion of shape memory alloy havinga cylindrical shape. The prosthesis comprises a backbone running along alongitudinal axis of the device and has ribs circumferentially extendingfrom the backbone. The device widens radially while maintaining asubstantially cylindrical shape at or above a transition temperature.

In this aspect of the invention, the shape memory material comprisingthe apparatus is a nickel-titanium alloy. Doping with copper or chromiumto adjust its response to temperature can further modify thenickel-titanium alloy.

In a fourth aspect of the invention, a penile prosthesis that isimplantable in the corpus cavernosum is disclosed wherein the penileprosthesis is comprised of a single portion of shape memory alloy havinga cylindrical shape. The prosthesis comprises a backbone running along alongitudinal axis of the device and has ribs circumferentially extendingfrom the backbone. The backbone is comprised of a plurality of holes ofa plurality of sizes and a plurality of shapes to provide a wider rangeof flexibility. The device widens radially while maintaining asubstantially cylindrical shape at or above a transition temperature.

In this aspect of the invention, the shape memory material comprisingthe apparatus is a nickel-titanium alloy. The nickel-titanium alloy canbe further modified by doping with copper or chromium to adjust itsresponse to temperature.

In a fifth aspect of the invention, a penile prosthesis that isimplantable in the corpus cavernosum is disclosed wherein the penileprosthesis is comprised of a single portion of shape memory alloy havinga cylindrical shape. The prosthesis comprises a backbone running along alongitudinal axis of the device and has ribs circumferentially extendingfrom the backbone. The device widens radially while maintaining asubstantially cylindrical shape at or above a transition temperature.

In this aspect of the invention, the shape memory material comprisingthe apparatus is a nickel-titanium alloy. The nickel-titanium alloy canbe further modified by doping with copper or chromium to adjust itsresponse to temperature.

In a fifth aspect of the invention, a penile prosthesis that isimplantable in the corpus cavernosum is disclosed wherein the prosthesisis comprised of a longitudinal axis, a backbone, and a plurality ofloops. The backbone is comprised of a shape memory alloy and exhibits aleft side and right side. The backbone is capable of maintaining anon-linear shape with respect to the longitudinal axis below atransition temperature, and is capable of substantially reverting to alinear shape defined by the longitudinal axis at or above a transitiontemperature.

The plurality of loops in this aspect of the invention may are comprisedof a shape memory alloy. The loops are attached to both the left sideand right side of the backbone and have an arcuate shape that defines acylindrical contour of the apparatus. The loops widen radially whilemaintaining a substantially cylindrical contour at or above a transitiontemperature.

In this aspect of the invention, the shape memory material comprisingthe backbone and the plurality of loops is a nickel-titanium alloy. Thenickel-titanium alloy can be further modified by doping with copper orchromium to adjust its response to temperature.

In an alternative of the fifth aspect of the invention, the plurality ofloops having an arcuate shape are comprised of a first section and asecond section. Both of these sections are able to define a cylindricalcontour of the apparatus. When the apparatus is exposed to a temperatureat or above the transition temperature, the first section widensradially while maintaining a substantially cylindrical contour and thesecond section radially contracts while maintaining a substantiallycylindrical contour.

In a sixth aspect of the invention, a penile prosthesis that isimplantable in the corpus cavernosum is disclosed wherein the prosthesisis comprised of a longitudinal axis, a backbone, and a plurality ofribs. The backbone is comprised of a shape memory alloy and exhibits aleft side and right side. The backbone is capable of maintaining anon-linear shape with respect to the longitudinal axis below atransition temperature, and is capable of substantially reverting to alinear shape defined by the longitudinal axis at or above a transitiontemperature.

The plurality of ribs in this aspect of the invention is comprised of ashape memory alloy. The ribs are attached to both the left side andright side of the backbone and have an arcuate shape that defines acylindrical contour of the apparatus. The ribs widen radially whilemaintaining a substantially cylindrical contour at or above a transitiontemperature.

In this aspect of the invention, the shape memory material comprisingthe backbone and the plurality of ribs is a nickel-titanium alloy. Thenickel-titanium alloy can be further modified by doping with copper orchromium to adjust its response to temperature.

In an alternative of the sixth aspect of the invention, the plurality ofribs having an arcuate shape is comprised of a first section and asecond section. Both of these sections define a cylindrical contour ofthe apparatus. When the apparatus is exposed to a temperature at orabove the transition temperature, the first section widens radiallywhile maintaining a substantially cylindrical contour and the secondsection radially contracts while maintaining a substantially cylindricalcontour.

In a seventh aspect of the invention, a penile prosthesis that isimplantable in the corpus cavernosum is disclosed wherein the prosthesisis comprised of a longitudinal axis, a backbone, and a plurality ofribs. The backbone is comprised of a shape memory alloy and exhibits aleft side and right side. The backbone is capable of maintaining anon-linear shape with respect to the longitudinal axis below atransition temperature, and is capable of substantially reverting to alinear shape defined by the longitudinal at or above a transitiontemperature.

The plurality of ribs in this aspect of the invention is comprised of ashape memory alloy. The ribs are attached to both the left side andright side of the backbone and have an arcuate shape that defines acylindrical contour of the apparatus. The ribs widen radially whilemaintaining a substantially cylindrical contour at or above a transitiontemperature.

In this aspect of the invention, the shape memory material comprisingthe backbone and the plurality of ribs is a nickel-titanium alloy. Thenickel-titanium alloy can be further modified by doping with copper orchromium to adjust its response to temperature.

In an alternative of the seventh aspect of the invention, the pluralityof ribs having an arcuate shape is comprised of a first section and asecond section. Both of these sections define a cylindrical contour ofthe apparatus. When the apparatus is exposed to a temperature at orabove the transition temperature, the first section widens radiallywhile maintaining a substantially cylindrical contour and the secondsection radially contracts while maintaining a substantially cylindricalcontour.

In an eighth aspect of the invention, a method of simulating an erectionof a penis is disclosed wherein an implanted penile prosthesiscomprising a shape memory alloy is heated to a temperature at which adimension of the prosthesis enlarges.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of a shape memory alloy hysteresis curve.

FIG. 2 is an example of a two-way shape memory alloy hysteresis curve.

FIG. 3 is an example of a penile prosthesis comprised of a singleportion of a shape memory alloy, has ribs in the shape of loops, andwherein the shape memory alloy is in an austenite phase.

FIG. 4 is an example of a penile prosthesis comprised of a singleportion of a shape memory alloy, has ribs in the shape of loops, andwherein the shape memory alloy is in a martensitic phase.

FIG. 5 is an example of a penile prosthesis comprised of a singleportion of a shape memory alloy, has ribs, and wherein the shape memoryalloy is in an austenite phase.

FIG. 6 is an example of a penile prosthesis comprised of a singleportion of a shape memory alloy, has ribs, wherein the shape memoryalloy is in a martensitic phase.

FIG. 7 is an example of a penile prosthesis comprised of a singleportion of a shape memory alloy, has ribs, and wherein the shape memoryalloy is in an austenite phase.

FIG. 8 is an example of a penile prosthesis comprised of a singleportion of a shape memory alloy, has ribs, and wherein the shape memoryalloy is in a martensitic phase.

FIG. 9 is an example of a penile prosthesis comprising a backbone madeof a shape memory alloy, ribs in the shape of loops comprised of a shapememory alloy wherein the loops must be attached to the backbone, andwherein the shape memory alloys are in an austenite phase.

FIG. 10 is an example of a penile prosthesis comprising a backbone madeof a shape memory alloy, ribs in the shape of loops comprised of a shapememory alloy wherein the loops must be attached to the backbone, andwherein the shape memory alloys are in a martensitic phase.

FIG. 11 is an example of a penile prosthesis comprising a backbone madeof a shape memory alloy, ribs in the shape of loops comprised of a shapememory alloy wherein the loops must be attached to the backbone, theprosthesis is in a martensitic phase, and the backbone is maintaining anon-linear shape with respect to a longitudinal axis of the device whilein the martensitic phase.

FIG. 12 is a depiction of an additional prosthesis comprising a core, anexoskeleton comprised of a shape memory alloy surrounding the core, anda heat-conducting sheath surrounding the exoskeleton and core.

FIG. 13 is a depiction of the core having different shaped ends.

FIG. 14 is a cross-section of the penis depicting the implantationlocation the penile prostheses disclosed herein.

FIG. 15 is an example of a penile prosthesis comprising a backbone witha plurality of holes of a plurality of sizes and shapes made of one waymemory alloy, also having ribs wherein the shape memory alloys are in amartensitic phase.

DETAILED DESCRIPTION

Prostheses for simulating a penile erection are disclosed herein. Theprostheses disclosed herein may comprise a shape memory alloy. As isgenerally understood in the engineering arts, a shape memory alloy maybe able to exhibit a shape recovery effect. The shape recovery aspect ofa shape memory alloy is associated with the martensitic transformation.When an alloy of steel is heated to an austenite phase and then rapidlycooled to a martensitic metallic phase, the metallic martensitic phaseremains upon heating over a small temperature range. In comparison, themartensitic transformation in a shape memory alloy is thermoelastic overa small temperature range. This means the martensitic metallic phase istransformed to the parent austenite metallic phase over a small increasein temperature, and then may be regained over a small decrease intemperature, (Shape-Memory Alloys, Kirk-Othmer Encyclopedia of ChemicalTechnology, downloaded Nov. 7, 2011).

The intermetallic phase in these alloys undergoes a displaced,shear-like transformation when cooled below a critical temperaturedesignated as M_(S) (martensitic start). Upon further cooling, to atemperature designated as M_(F) (martensitic finish), the transformationis complete and the alloy is said to be in a martensitic state. Whenthis martensitic is deformed, it undergoes a strain that is recoveredwhen the alloy is heated. This recovery process starts at anothercritical temperature designated as A_(S) (austenite start) and iscompleted at a higher temperature A_(F) (austenite finish),(Shape-Memory Alloys, Kirk-Othmer Encyclopedia of Chemical Technology,downloaded Nov. 7, 2011).

There is a hysteresis associated with the formation of the martensiticmetallic phase and its reverse transformation to the parent austenitemetallic phase in a shape memory alloy. The temperatures M_(S), M_(F),A_(S), and A_(F) may depend on the particular base alloy. In a preferredembodiment of an invention disclosed herein, the base alloy may be acopper-aluminum-nickel alloy. The copper-aluminum-nickel alloy disclosedherein may be between about 28.00 atomic percent aluminum and 29.00atomic percent aluminum, about 3.00 atomic percent nickel and about 4.00atomic percent nickel, the balance copper. In a more preferredembodiment of an invention disclosed herein, the base alloy may be anickel-titanium alloy. The nickel-titanium alloy disclosed herein may bebetween about 49.00 atomic percent nickel and about 51.00 atomic percentnickel, the balance titanium.

The temperatures M_(S), M_(F), A_(S), and A_(F) may also depend on theaddition of an additive to the base alloy. In a preferred embodiment ofthe invention disclosed herein, the additive may be chromium. In thispreferred embodiment, the amount of chromium may be between about 0.00atomic percent and about 10.00 atomic percent of the base alloy'scomposition. In an alternative preferred embodiment of an inventiondisclosed herein, the additive may be copper. In this alternativepreferred embodiment of an invention disclosed herein, the amount ofcopper may be between about 0.00 atomic percent and about 5.00 atomicpercent of the base alloy's composition. In a further alternativepreferred embodiment of an invention disclosed herein, the additive maybe both chromium and copper. In this further alternative preferredembodiment, the amount of chromium may vary between about 0.00 atomicpercent and about 10.00 atomic percent of the base alloy's composition,and the copper may vary between about 0.00 atomic percent and about 5.00atomic percent of the base alloy's composition.

Shape memory alloys may exhibit two types of shape memory effects. Thefirst, known as the shape memory effect, refers to the phenomenonwherein a shape memory alloy exposed to a mechanical deformation“remembers” and returns to pre-set shape upon exposure to heat. Torepeat this event, the shape memory alloy must be cooled andmechanically deformed before it can return to its pre-set shape. Incomparison, in a two-way shape memory effect the material can cyclebetween two pre-set shapes upon heating or cooling without mechanicaldeformation. For purposes of this disclosure, alloys exhibiting theshape memory effect are known as “shape memory alloys,” and alloysexhibiting the two-way shape memory effect are known as “two-way shapememory alloys.”

In a preferred embodiment a prosthesis disclosed herein may comprise ashape memory alloy. Referring to FIG. 1, in a preferred embodiment aprosthesis disclosed herein may exhibit a hysteresis curve comprisingA_(F) 1, M_(S) 2, M_(F) 3, and A_(S) 4. As demonstrated in FIG. 1, A_(F)is set above resting penile temperature. In this state, the prosthesisis substantially, if not completely, in its pre-set non-mechanicallydeformed shape. In this state, the implanted penile prosthesis may beable to impart expansive forces to the penile corpus cavernosa andtunica albuginea, and the penis may exhibit the increased radial andlongitudinal growth experienced by an erect penis. In this state, thepenis may appear erect.

Still referring to FIG. 1, an implanted prosthesis may then be exposedto a first-transition temperature 5 that coincides with M_(S) 2. Asdemonstrated in FIG. 1, the first-transition temperature may be setbelow penile resting temperature. In a preferred embodiment, thefirst-transition temperature is between about 20 degrees Celsius andabout 32 degrees Celsius. In this state, the amount of the alloy in theaustenite phase begins to decrease and the amount of the alloy in themartensitic phase begins to increase. As the amount of the alloy in themartensitic phase begins to increase, the prosthesis may be able tobegin losing its pre-set shape. As the temperature continues todecrease, the amount of the alloy in the martensitic phase increasesuntil the prosthesis is substantially, if not completely, comprised of amartensitic phase. This point is denoted at M_(F) 3. In this state, theprosthesis may be mechanically deformed. Since the prosthesis isimplanted in the penile corpus cavernosa, the innate compressive forcesof the penile corpus cavernosa may lead to mechanical deformation of theprosthesis. Alternatively, compressive forces from the tunica albugineamay lead to mechanical deformation. Additionally, deformation may beimparted through manipulation by the hands. In this state, the implantedprostheses impart less expansive forces to the penile corpus cavernosaand tunica albuginea than compared to the austenite phase and the penismay not exhibit the increased radial and longitudinal growth exhibitedby an erect penis. Instead, the penis may appear flaccid and may be ableto be discretely tucked away.

Still referring to FIG. 1, a penile prosthesis may then be exposed to asecond-transition temperature 6 that coincides with A_(S) 4. Asdemonstrated in FIG. 1, the second-transition temperature may be setabove resting penile temperature. In a preferred embodiment, thesecond-transition temperature is between about 35 degrees Celsius andabout 45 degrees Celsius. In this state, the amount of the alloy in theaustenite phase begins to increase and the amount of the alloy in themartensitic phase begins to decrease. As the amount of the alloy in theaustenite phase increases, the prosthesis begins to remember its pre-setshape. As the temperature continues to increase, the amount of the alloyin the austenite phases continues to increase until the prosthesis issubstantially, if not completely, comprised of an austenite phase. Thisstate is denoted in FIG. 1 as A_(F) 1. The prosthesis in this state issubstantially, if not completely, in its pre-set non-mechanicallydeformed shape. In this state, the implanted penile prosthesis may beable to impart expansive forces to the penile corpus cavernosa andtunica albuginea, and the penis may exhibit the increased radial andlongitudinal growth experienced by an erect penis. In this state, thepenis may appear erect.

In an alternative embodiment, the prostheses disclosed herein maycomprise a two-way shape memory alloy. Referring to FIG. 2, in thealternative embodiment the prostheses disclosed herein may exhibit atwo-way hysteresis curve. Referring to FIG. 2, in this alternativeembodiment the prosthesis disclosed herein may exhibit a two-wayhysteresis curve comprising A_(F) 7, M_(S) 8, M_(F) 9, and A_(S) 10. Asdemonstrated in FIG. 2, A_(F) is set above resting penile temperature.In this state, the prosthesis may comprise a first pre-set shape. Inthis state, the implanted penile prosthesis may be able to impartexpansive forces to the penile corpus cavernosa and tunica albuginea,and the penis may exhibit the increased radial and longitudinal growthexperienced by an erect penis. In this state, the penis may appearerect.

Still referring to FIG. 2, an implanted prosthesis may then be exposedto a first-transition temperature 11 that coincides with M_(S) 8. Asdemonstrated in FIG. 1, the first-transition temperature may be setbelow penile resting temperature. In a preferred embodiment, thefirst-transition temperature is between about 20 degrees Celsius andabout 32 degrees Celsius. In this state, the amount of the alloy in theaustenite phase begins to decrease and the amount of the alloy in themartensitic phase begins to increase. As the amount of the alloy in themartensitic phase begins to increase, the prosthesis may be able tobegin losing its first pre-set shape and begins to remember a secondpre-set shape. As the temperature continues to decrease, the amount ofthe alloy in the martensitic phase increases until the prosthesis issubstantially, if not completely, comprised of a martensitic phase. Thispoint is denoted at M_(F) 9. In this state, the prosthesis is in itssecond pre-set shape. In this state, the implanted prostheses impartless expansive forces to the penile corpus cavernosa and tunicaalbuginea than compared to the austenite phase and the penis may notexhibit the increased radial and longitudinal growth exhibited by anerect penis.

Still referring to FIG. 2, a penile prosthesis may then be exposed to asecond-transition temperature 12 that coincides with A_(S) 10. Asdemonstrated in FIG. 2, the second-transition temperature may be setabove resting penile temperature. In a preferred embodiment, thesecond-transition temperature is between about 35 degrees Celsius andabout 45 degrees Celsius. In this state, the amount of the alloy in theaustenite phase begins to increase and the amount of the alloy in themartensitic phase begins to decrease. As the amount of the alloy in theaustenite phase increases, the prosthesis begins to remember its firstpre-set shape. As the temperature continues to increase, the amount ofthe alloy in the austenite phases continues to increase until theprosthesis is substantially, if not completely, comprised of anaustenite phase. This state is denoted as in FIG. 2 as A_(F) 7. Theprosthesis in this state is substantially, if not completely, in itsfirst pre-set shape. In this state, the implanted penile prosthesis maybe able to impart expansive forces to the penile corpus cavernosa andtunica albuginea, and the penis may exhibit the increased radial andlongitudinal growth experienced by an erect penis. In this state, thepenis may appear erect.

Referring to FIGS. 3 through 8, a penile prosthesis disclosed herein maybe comprised of a single sheet 13 of a shape memory alloy. The penileprosthesis comprised of a single sheet 13 of memory alloy can be madethrough various methods. Memory alloy can be cut to a preferredembodiment by methods using but not limited to a laser, a water jet, ora cast molding. In a preferred embodiment the prosthesis may have asubstantially cylindrical shape. The sheet may have a longitudinal axis14 running through the length of the prosthesis, and a backbone 15running with the longitudinal axis. While the transition temperaturebetween flaccid/martensitic state and rigid/austenitic state is mostlydictated by the memory alloy properties, the level of flexibility andrigidity is regulated by the geometry of the prosthesis. Referring toFIG. 15, adding or removing memory alloy from the backbone can changethe flexibility of the penile prosthesis. More specifically, flexibilitycan be changed by creating holes 37 in the prosthesis backbone. Holes 37could comprise various sizes in surface area as long as not to exceedthe surface area of the backbone 15 memory alloy. Holes 37 could alsocomprise various shapes including; squares, circles, ovals, rectangles,and diamonds. Additionally the backbone 15 widths may be altered toincrease or decrease flexibility. The backbone 15 width should be equalto or less than one half the circumference of the cylindrical outercontour 40. The device may comprise at least two ribs 16circumferentially extending from the backbone in a direction opposite toa circumferential extension of at least one adjacent rib.

Referring to FIGS. 3 and 4, in a preferred embodiment the ribs 16 mayhave the profile of a loop. The defining characteristics of this loopare that it has a first-end 17 and a second-end 18, and that both thefirst-end and second-end are continuous with the backbone 15. The mayhave any arcuate shape that defines a cylindrical contour of theprosthesis.

Referring to FIGS. 5 and 6, in an alternative embodiment the ribs 16 mayhave the profile of a rib. The defining characteristics of a rib arethat it has a first-end 19, a second-end 20, a width 21 greater than orequal to the distance between the first-end and second-end, and thatonly the first-end is in continuous communication with the backbone 15.The ribs may have any arcuate shape that defines a cylindrical contourof the prosthesis.

Referring to FIGS. 7 and 8, in an alternative embodiment the ribs 16 mayhave the profile of a whisker. The defining characteristics of a whiskerare that is has a first-end 22, a second-end 23, a width 24 less thanthe distance between the first-end and second-end, and that only thefirst-end is in continuous communication with the backbone 15. The ribsmay have an arcuate shape that defines a cylindrical contour of theprosthesis.

Since the prostheses depicted in FIGS. 3 through 8 and FIG. 15 may becomprised of a shape memory alloy, they may exhibit the hysteresisdepicted in FIG. 1. FIGS. 3, 5, and 7 depict the penile prostheses inthe austenite state at or above A_(F) 1. In this state, the prosthesesare substantially, if not completely, in their pre-set non-mechanicallydeformed shape. A defining characteristic of this shape is that it has asubstantially, if not completely, cylindrical outer contour. While notnecessary, an additional characteristic of the prostheses in theaustenite state is that the ribs 16 do not interleave with one another.FIGS. 4, 6, and 8 depict the penile prostheses in a martensitic state ator below M_(F) 3. In this state, the prostheses are substantially, ifnot completely, in their mechanically deformed shape and the ribs mayinterleave with one another.

Referring to FIGS. 1, 3, 5, and 7, in one mode of operation theprosthesis begins in an austenite state at or above A_(F) 1. It is thenexposed to a transition temperature M_(S) 2, below A_(F), at which pointthe amount of alloy in the martensitic phase begins increasing and theamount of the alloy in the austenite phase begins decreasing. Referringthe FIGS. 1, 4, 6 and 8, the prosthesis is then further exposed todecreasing temperatures until it reaches M_(F) 3, at which point thealloy is substantially, if not completely, comprised of a martensiticphase. In this state the prosthesis may be mechanically deformed and theribs 16 may interleave with one another. Referring to FIGS. 1, 3, 5, and7, the prosthesis may then be exposed to another transition temperatureA_(S) 4, above M_(F), at which point the amount of alloy in themartensitic phase begins decreasing, the amount of the alloy in theaustenite phase begins increasing, and the prosthesis begins to widenradially while maintaining a substantially cylindrical outer contour. Asthe temperature continues increasing, the amount of the alloy in theaustenite phase continues increasing, and the prosthesis continues towiden radially while maintaining a substantially cylindrical outercontour until reaching A_(F). At this point, the alloy is substantially,if not completely, comprised of austenite; the prosthesis stops wideningradially; and the prosthesis is in its pre-set non-mechanically deformedshape.

Referring to FIGS. 9 through 11, an additional penile prosthesisdisclosed herein may be comprised of a backbone 25 and a plurality ofribs 26. In a preferred embodiment the backbone may be comprised of afirst shape memory alloy. The backbone may further be comprised of aleft-side 27 and a right-side 28, and define a longitudinal axis 29running through the device. The plurality of ribs may be attached toboth the left side and the right side of the backbone and may beattached to the backbone by soldering or by welding.

Still referring to FIGS. 9 through 11, in a preferred embodiment theribs 26 may be comprised of a shape memory alloy. In a preferredembodiment, the shape memory alloy comprising the ribs is the same asthe shape memory alloy comprising the backbone 25. In an alternativeembodiment, the shape memory alloy comprising the ribs is different thanthe shape memory alloy comprising the backbone. In an alternativeembodiment, the ribs may be comprised of a two-way shape memory alloy.

Still referring to FIGS. 9 through 11, in a preferred embodiment theribs 26 may have the profile of a loop. The defining characteristics ofa loop are that it has a first-end 30 and a second-end 31, and that boththe first-end and second-end are attached to the backbone 25. The loopsmay have an arcuate shape that defines a cylindrical contour of theprosthesis.

Referring to FIG. 15, in a preferred embodiment of the penileprosthesis, the memory alloy backbone 38 may have various holes 37 ofvarious sizes in various shapes which provide more flexibility to theoverall structure of the device. Holes 37 could comprise various shapesincluding; squares, circles, ovals, rectangles, and diamonds The ribs 39may have the profile of a rib with a circular closer at eachlongitudinal end of the device 40. The defining characteristics of a ribare that it has a first-end 39, a second-end 39, a width 39 greater thanor equal to the distance 41 between the first-end and second-end, andthat only the first-end is in continuous communication with the backbone38. The ribs may have any arcuate shape that defines a cylindricalcontour of the prosthesis.

Since the prosthesis depicted in FIGS. 9 through 11 may be comprised ofa shape memory alloy, it may exhibit the hysteresis depicted in FIG. 1.FIG. 9 depicts the penile prostheses in the austenite state at or aboveA_(F) 1. In this state, the prosthesis is substantially, if notcompletely, in its pre-set non-mechanically deformed shape. A definingcharacteristic of this shape is that the outer contour is substantially,if not completely, cylindrical. While not necessary, an additionalcharacteristic of the prostheses in the austenite state is that the ribs16 do not overlap. Additionally, the backbone 25 in this state issubstantially linear with respect to the longitudinal axis and is ableto withstand a compressive load of about 1.50 kilograms or less, DanielUdelson, “Biomechanics of male erectile function,” 4 J. R. Soc.Interface 1039, 1031-1048, (2007). FIGS. 10 and 11 depict the penileprosthesis in a martensitic state at or below M_(F) 3. In this state,the prosthesis is substantially, if not completely, in its mechanicallydeformed shape. While not necessary, an additional characteristic of theprostheses in the martensitic state is that the ribs 16 interleave withone another. As depicted in FIG. 11, an additional characteristic of theprosthesis in the martensitic state is that the backbone may be capableof maintaining a nonlinear shape with respect to the longitudinal axis29.

Referring to FIGS. 1 and 9, in one mode of operation the prosthesisbegins in an austenite state at or above A_(F) 1. Then it is exposed toa transition temperature M_(S) 2, less then A_(F), at which point theamount of alloy in the martensitic phase begins increasing and theamount of the alloy in the austenite phase begins decreasing. Referringto FIGS. 1, and 10 through 11, the prosthesis is then further exposed todecreasing temperatures until it reaches M_(F) 3, at which point thealloy is substantially, if not completely, comprised of a martensiticphase. In this state the prosthesis may be mechanically deformed and theribs 16 may interleave with one another. As depicted in FIG. 11, thebackbone may have a non-linear shape with respect to the longitudinalaxis 29 in this state. Referring to FIGS. 1 and 9, the prosthesis maythen be exposed to another transition temperature A_(S) 4, above M_(F),at which point the amount of alloy in the martensitic phase beginsdecreasing, the amount of the alloy in the austenite phase beginsincreasing, and the prosthesis begins to widen radially whilemaintaining a substantially cylindrical shape outer contour. As thetemperature continues increasing, the amount of the alloy in theaustenite phase continues increasing, and the prosthesis continues towiden radially while maintaining a substantially cylindrical contouruntil reaching A_(F). At this point, the alloy is substantially, if notcompletely, comprised of austenite; the prosthesis stops wideningradially; and the prosthesis is in its pre-set non-mechanically deformedshape.

The pre-set non-mechanically deformed shape of the ribs does notnecessarily need to lead to a radial widening of the prosthesis. Thepre-set shape of the ribs may also lead to a radial contraction ofprosthesis, or a portion of the prosthesis. In an alternative embodiment(NOT SHOWN), the ribs may have a first section and a second section. Thefirst section may widen radially while maintaining a substantiallycylindrical outer contour and the second section may contract radiallywhile maintaining a substantially cylindrical contour. Alternatively,the ribs may comprise a third section, the third section alsocontracting. The third section contracts to a greater degree than thesecond section and maintains a substantially cylindrical outer contour.

Referring to FIGS. 12 and 13, prosthesis implantable in the corpuscavernosa disclosed herein may further comprise a core 32 surrounded byan exoskeleton 33 comprised of a shape memory alloy. The core andexoskeleton may be further surrounded by a sheath 34 of heat-conductingstretchable material. In a preferred embodiment the core is comprised ofsaline. In a more preferred embodiment, the core may be comprised of aheat-retaining gel. In an even more preferred embodiment, the core maybe comprised of a biocompatible heat-retaining gel. In a preferredembodiment, the exoskeleton is comprised of a nickel-titanium shapememory alloy disclosed herein.

Referring to FIG. 13, the core 32 may comprise a first-end 35 and asecond-end 36. In a preferred embodiment, the first-end may have anoutward-facing convex shape. In a preferred embodiment, the second-endmay have an outward-facing substantially conical shape.

Referring to FIG. 14, a prosthesis disclosed herein may be implanted ina penile corpus cavenosa. In use, at least one prosthesis as disclosedherein is implanted in each penile corpus cavernosa through a skinincision after dilatation of the corporal bodies is achieved.

In use, the entire prosthetic apparatus comprises of 2 erective bodiesthat are inserted in the compora cavernosa of the penis. In theaustenitic state each erective body is able to withstand at least 1.50kilograms in the axial direction without buckling. Such a force levelhas been shown in the literature to be sufficient to the naturalerective body (the penis) for coitus, Daniel Udelson, “Biomechanics ofmale erectile function,” 4 J. R. Soc. Interface 1039, 1031-1048, (2007).The design of the prosthesis is such that one erective body (out of two)could be sufficient for coitus. The prosthesis claimed herein was testedusing an Instron machine. An Instron machine is able to measure thedisplacement and the force generated on a sample for a specific periodof time. The prosthesis claimed exhibited properties capable ofwithstanding a force of at least 1.5 kilograms in the axial directionwithout buckling.

In use, beginning from a flaccid state, a heat source such as a warmpack having a temperature greater than or equal to about the A_(F) ofthe shape memory alloy is placed over the penis. Over time there is heattransfer to the implanted prosthesis and the temperature of the shapememory alloy rises above penile resting temperature, continues toincrease above the A_(S) of shape memory alloy, and continues increasinguntil the shape memory alloy reaches A_(F). In this configuration animplanted prosthesis is in its erect conformation and intercourse mayensue. The structural mechanical design of the prosthesis and its superelastic properties are such that the erective body is able to maintainits structural shape during normal force of coitus by elasticallybuttressing the corpora cavernosa. After coitus, the penis is thenactively cooled with an ice pack or shower. Over time there is heatremoval from the implanted prosthesis and the temperature of the shapememory alloy decreases below penile resting temperature, continues todecrease below M_(S) of the shape memory alloy, and continues todecrease until the shape memory alloy reaches M_(F). In thisconfiguration the penis is in a flaccid state, and may be discretelytucked away.

It should be understood that the methods, procedures, operations,devices, and systems illustrated in FIGS. 1 through 14 may be modifiedwithout departing from the spirit of the invention. For example, thesemethods, procedures, operations, devices, and systems may comprise moreor fewer steps or components than appear herein, and these steps orcomponents may be combined with one another, in part or in whole.

Furthermore, the present disclosure is not to be limited in terms of theparticular embodiments described in this application, which are intendedas illustrations of various aspects. Many modifications and variationscan be made without departing from its spirit and scope, as will beapparent to those skilled in the art. Functionally equivalent methodsand apparatuses within the scope of the disclosure, in addition to thoseenumerated herein will be apparent to those skilled in the art from theforegoing descriptions.

It is to be understood that this disclosure is not limited to particularmethods, reagents, compounds compositions or biological systems, whichcan, of course, vary. It is also to be understood that the terminologyused herein is for the purpose of describing particular embodimentsonly, and is not intended to be limiting. With respect to the use ofsubstantially any plural and/or singular terms herein, those havingskill in the art can translate from the plural to the singular and/orfrom the singular to the plural as is appropriate to the context and/orapplication. The various singular/plural permutations may be expresslyset forth herein for sake of clarity.

It will be understood by those within the art that, in general, termsused herein are intended as “open” terms (e.g., the term “including”should be interpreted as “including but not limited to,” the term“having” should be interpreted as “having at least,” the term “includes”should be interpreted as “includes but is not limited to,” etc.).

Furthermore, in those instances where a convention analogous to “atleast one of A, B, and C, etc.” is used, in general such a constructionis intended in the sense one having skill in the art would understandthe convention (e.g., “a system having at least one of A, B, and C”would include but not be limited to systems that have A alone, B alone,C alone, A and B together, A and C together, Band C together, and/or A,B, and C together, etc.). It will be further understood by those withinthe art that virtually any disjunctive word and/or phrase presenting twoor more alternative terms, whether in the description or figures, shouldbe understood to contemplate the possibilities of including one of theterms, either of the terms, or both terms. For example, the phrase “A orB” will be understood to include the possibilities of “A” or “B” or “Aand B.”

As will be understood by one skilled in the art, for any and allpurposes, such as in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc.

As will also be understood by one skilled in the art, all language suchas “up to,” “at least,” “greater than,” “less than,” and the likeinclude the number recited and refer to ranges which can be subsequentlybroken down into subranges as discussed above.

Finally, as will be understood by one skilled in the art, a rangeincludes each individual member. Thus, for example, a group having 1-3members refers to groups having 1, 2, or 3 members. Similarly, a grouphaving 1-5 members refers to groups having 1,2,3,4, or 5 members, and soforth.

What is claimed is:
 1. A penile prosthesis implantable in the corpuscavernosum comprising: a) a shape memory alloy having a dimension thatenlarges radially in response to an increase in temperature around saidprosthesis; and b) a cylindrical outer contour along its longitudinalaxis.
 2. The penile prosthesis of claim 1, wherein the longitudinal axisof the cylindrical outer contour comprises: a) a backbone comprising ashape memory alloy and; b) at least two ribs comprising a shape memoryalloy.
 3. The penile prosthesis of claim 1, wherein the shape memoryalloy comprises a thickness less than about two millimeters.
 4. Thepenile prosthesis of claim 1, further comprising a heat-conductingsheath.
 5. The penile prosthesis of claim 2, wherein the ribs widenradially while maintaining substantially cylindrical contour at or abovea transition temperature.
 6. The penile prosthesis of claim 2, whereinthe backbone reverts to a linear shape defined by said longitudinal axisat or above a transition temperature.
 7. The penile prosthesis of claim2, wherein the backbone maintains a non-linear shape with respect tosaid longitudinal axis at a temperature below a transition temperature.8. The penile prosthesis of claim 2, wherein the backbone comprises awidth equal to or less than one half the circumference of saidcylindrical outer contour.
 9. The penile prosthesis of claim 2, whereinthe backbone comprises holes, wherein the surface area of said holesdoes not exceed the surface area of said shape memory alloy of saidbackbone.
 10. The penile prosthesis of claim 2, further comprising aheat-conducting sheath.
 11. The penile prosthesis of claim 2, whereinthe backbone comprises a left side and a right side.
 12. The penileprosthesis of claim 11, wherein the ribs are attached to both the rightside and left side of said backbone having a substantially arcurateshape defining a cylindrical contour of the penile prosthesis.
 13. Amethod of simulating an erection of a penis comprising heating a penileprosthesis comprising a shape memory alloy to a temperature at which adimension of the prosthesis enlarges radially.
 14. The method of claim13, wherein the shape memory alloy comprises a shape memory alloy. 15.The method of claim 13, wherein the penile prosthesis has a cylindricalouter contour comprising: a) a backbone, and b) at least two ribsattached to the backbone, wherein the cylindrical outer contour alongits longitudinal axis can withstand at least 1.5 kilograms of forcewithout buckling.
 16. The method of claim 13, wherein the penileprosthesis further comprises a heat-conducting sheath.
 17. A method ofcreating an erection of a penis implanted with a penile prosthesis,comprising heating the penile prosthesis comprising a shape memory alloyto a temperature at which the prosthesis enlarges radially.
 18. Themethod of claim 17, wherein the penile prosthesis has a cylindricalouter contour comprising: a) a backbone, and b) at least two ribsattached to the backbone, wherein the cylindrical outer contour alongits longitudinal axis can withstand at least 1.5 kilograms of forcewithout buckling.
 19. The method of claim 17, wherein the penileprosthesis further comprises a heat-conducting sheath.